DESCRIPTION: This renewal proposal focuses on the signal transduction pathways that modulate hepatocyte gene expression and proliferation through site-specific phosphorylations of C/EBP-beta. Preliminary results show that TGF-alpha and phorbol esters/PKC-alpha mediate their effects on hepatocyte proliferation, at least in part, through the activation of ribosomal S6-kinase and phosphorylation of C/EBP-beta on its activation domain. In addition, cachexia and TNF-alpha inhibit albumin transcription, at least in part, throug an oxidative stress/NO cascade resulting in the activation of stress-activated protein (SAP)- kinase and phosphorylation of C/EBP-beta on its basic domain, which abolishes the binding of C/EBP-beta to the albumin enhancer/promoter DNA sequence. The specific aims are 1) assess the role of phosphorylation on hepatocyte proliferation, 2) examine the modulation of hepatocyte proliferatio in C/EBP-beta mice, 3) examine the regulation of the cell cycle by C/EBP-beta in hepatocytes, 4) assess the role of oxidative stress and NO on C/EBP-beta phosphorylation and inhibition of albumin transcription induced by cachexia an TNF-alpha, 5) examine the modulation of albumin expression in C/EBP-beta transgenic mice, and 6) examine the mechanisms that induce decreased albumin expression in human cachexia.